1. Field of the Invention
The present invention relates to a sensor system, more particularly to an sensor system that is to be applied in a sensor device in order to adjust the sensitivity of the sensor device.
2. Description of the Prior Art
In the prior art technology, the sensitivity of a sensor system is usually adjusted through the magnitude of an operation amplifier so as to change the sensitivity of the sensor system. Therefore, by adjusting a variable resistor and change the magnitude of the operation amplifier, thereby achieving the sensitivity of the sensor system.
Referring to FIG. 1, a circuit diagram of the prior sensor system 1 is shown to include a voltage supply VCC coupled electrically to a resistor R1, a voltage contact P1, a resistor R2, a voltage contact P2, a resistor R3, a voltage contact P3, a resistor R4 and a GND (ground) contact, wherein, the voltage contacts P1, P2, P3 respectively have a first voltage V1, a second voltage V2 and a third voltage V3.
The operation amplifier 11 has an input end coupled electrically to an input signal source 2, which generates an input signal S1 into the input end of the operation amplifier 11 so as to be amplified thereby.
The operation amplifier 12 has an input end coupled electrically to the voltage contact P2, another input end coupled electrically to the output end of the operation amplifier 11, by a variable resistor VR and based on the second voltage V2 to adjust the magnitude of the operation amplifier 12, thereby adjusting the bias DC and the fluctuation bias voltage of the input signal S1 to generate an adjustment signal S2.
The operation amplifiers 13, 14 and an Or gate 15 are coupled together to form a window-type comparator, wherein an input end of the operation amplifier 13 is coupled electrically to the voltage contact P1, another input end thereof is coupled electrically to the output end of the operation amplifier 12 so that the operation amplifier 13 obtains a first voltage V1 and the fluctuation bias voltage of the adjustment signal S2. The operation amplifier 14 has an input end coupled electrically to the voltage contact P3, another input end thereof is coupled electrically to the output end of the operation amplifier 12 so that the operation amplifier 14 obtains a third voltage V3 and the fluctuation bias voltage of the adjustment signal S2. In addition, one input end of the Or gate 15 is coupled electrically to the output end of the operation amplifier 13, another input end thereof is coupled electrically to the output end of the operation amplifier 14 so as to determine whether the fluctuation bias voltage of the adjustment signal S2 is located within a standby voltage region defined cooperatively by the first and third voltages V1 and V3.
When the fluctuation bias voltage of the adjustment signal S2 is located outside of the standby voltage region defined cooperatively by the first and third voltages V1 and V3, the sensor system 1 generates a triggering signal S3.
FIG. 2A shows a voltage-time graph of the adjustment signal S2 when the prior art sensor system 1 is at the predetermined sensitivity. Also referring to FIG. 1 and as illustrated, the first, second and third voltages V1, V2 and V3 are 1.2 volts, 1 volts and 0.8 volt respectively. The first and third voltages V1 and V3 cooperatively define a standby voltage region of 0.4 volts. Therefore, as shown in FIG. 2A, the fluctuation bias voltage of the adjustment signal S2 is located three times outside of the standby voltage region defined cooperatively by the first and third voltages V1 and V3. Thus, the triggering signal S3 is generated three times.
FIG. 2B shows a voltage-time graph of the adjustment signal S2 after lowering the sensitivity of the prior art sensor system 1. Also referring to FIG. 1, when it is desired to lower the sensitivity of the sensor system 1, a variable resistor VR is applied to alter the magnitude of the operation amplifier 12 so as to adjust the fluctuation bias voltage of the adjustment signal S2 to be smaller than that shown in FIG. 2A. Therefore, in FIG. 2B, the fluctuation bias voltage of the adjustment signal S2 is located outside of the standby voltage region defined cooperatively by the first and third voltages V1 and V3 only once. Thus, only a single triggering signal S3 is generated.
FIG. 2C shows a voltage-time graph of the adjustment signal S2 after raising the sensitivity of the prior art sensor system 1. Also referring to FIG. 1, when it is desired to raise the sensitivity of the sensor system 1, a variable resistor VR is applied to alter the magnitude of the operation amplifier 12 so as to alter the fluctuation bias voltage of the adjustment signal S2 to be greater than that shown in FIG. 2A. Therefore, in FIG. 2C, the fluctuation bias voltage of the adjustment signal S2 is located outside of the standby voltage region defined cooperatively by the first and third voltages V1 and V3 6 times. Thus, the triggering signal S3 is generated six times.
In the prior art technology, a variable resistor VR is applied to alter the magnitude of the operation amplifier 12, which, in turn, changes the sensitivity of the sensor system 1. However, in using this method, a larger layout area in the printed circuit board is required in the sensor system 1. In addition, because the variable resistor VR itself is a kind of mechanical electronic element, it is susceptible to damage after multiple and repeated operations, thereby increasing the expense for the several numbers of the variable resistors VR.
On this respect, the inventor is indeed necessary to develop a new sensitivity sensor system in order to overcome these problems.